1,720,984 research outputs found
On the emergence of reciprocity gaps during interference pumping tests in unconfined aquifers
No full textWe present a theoretical analysis of the conditions under which reciprocity gaps between vertically-averaged (square) drawdowns can be observed during typical interference pumping tests performed in unconfined heterogeneous aquifers. This work expands on the analysis of Delay et al. [2011] and indicates that reciprocity gaps between vertically-averaged heads monitored during two consecutive tests can be due to vertical trends in aquifer properties (i.e., hydraulic conductivity and specific storage). These are then reflected in the vertical averaging procedure which is performed within a screened borehole and give rise to different observed dynamics of the averaged system responses. Spatially distributed recharge reflecting drainage from the unsaturated region during pumping can also significantly contribute to non-reciprocal behavior, especially for large test durations. Our theoretical findings are then illustrated through a suite of numerical simulations under a variety of vertical distributions of hydraulic parameters and in the presence of saturated/unsaturated flow conditions. We conclude that proper identification of the causes underlying reciprocity gaps can significantly enhance our conceptual understanding of the system response to a sequence of pumping stresses
Characterization of the Hydrogeological Experimental Site of. Poitiers (France) by stochastic well testing analysis
No full textWe assess the applicability and performance of the stochastic well testing methodology of Neuman et al. (2004, 2007) to provide a geostatistical characterization of the transmissivity distribution of a heterogeneous aquifer. We use cross-hole pumping test information (also referred to as interference testing) collected during two extensive and detailed experimental campaigns performed in 2004 and 2005 in a limestone aquifer constituting the Hydrogeological Experimental Site (HES) of Poitiers, France. The methodology we use is based on stochastic type-curves of mean drawdown and associated variance and is aimed at revisiting the results of routine pumping tests within a stochastic framework. It allows estimating the geometric mean, integral scale, and variance of local log-transmissivities on the basis of quasi steady state head data when a randomly heterogeneous confined aquifer is pumped at a constant rate. The results are discussed by comparison against (a) previous deterministic analyses performed at the site using the same dataset and (b) information obtained by geostatistical analysis of existing geophysical data. The estimated values of integral scales and variance of log-transmissivity are viewed in light of multiscale theories which conceptualize the heterogeneity of porous and fractured systems as hierarchical random processes distributed across a multiplicity of scales. The scale dependence observed for the estimated variogram parameters of log-transmissivity at the HES site is consistent with the behavior of published worldwide data
Theoretical analysis and field evidence of reciprocity gaps during interference pumping tests
No full textWe address the question of the reciprocity of drawdowns observed during a sequence of interference pumping tests performed within a porous medium, in the context of different conceptual models of subsurface flow. We provide a generalization of the work by Bruggeman (1972), extending his results obtained in 1972 for Darcian flows in an unbounded, heterogeneous porous medium. We then analyze reciprocity within a dual-continuum conceptualization, where the medium is viewed as being composed of two overlapping continua, representing the porous matrix and embedded fractures, respectively. We show theoretically, and demonstrate numerically, that only drawdowns associated with the fracture continuum display reciprocity under transient flow conditions. Conversely, non-flowing matrix and fracture continua display reciprocity behavior under steady-state conditions. We then provide field evidence of the insurgence of reciprocity gaps by analyzing interference test data from the karstic limestone aquifer of the Hydrogeological Experimental Site (HES) in Poitiers, France. On the basis of our theoretical results and experimental observations, we discuss different interpretations of the observed reciprocity gaps. These include (a) non-linear dependencies of local hydraulic parameters, (b) occurrence of internal boundaries within the domain, (c) inertial effects that develop through open conduits within the rock matrix, (d) modifications of the aquifer properties between subsequent pumping tests, and (e) significant contribution of the matrix pressure in monitored wells when the behavior of the aquifer is conceptualized by a dual-continuum approach
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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